IWRA Proceedings

AbstractThe persistent climate warming has led to an increased frequency of droughts accompanied by high temperatures in many regions of the globe, which is defined as a hotter drought. When precipitation remains stable, a hotter drought can intensify the drought severity by increasing surface evapotranspiration. The dual stress of high temperature and drought on vegetation ecosystems is more destructive to vegetation health and poses a serious threat to the ecological environment and socio-economic systems. The impact of hotter drought on terrestrial vegetation ecosystems varies in different climatic and vegetation zones and is affected by vegetation types and local geographical conditions. There is an urgent need to explore the complex response of the world’s major vegetation ecosystems to such hotter droughts in the context of global warming, so as to provide a basis for ecological protection and climate change response in various regions. In this study, the effects of hotter drought on terrestrial vegetation ecosystems in multiple study domains at different spatial and temporal scales were investigated based on remotely sensed vegetation indices and hydroclimatic data, using integrated methods such as common statistical analysis, machine learning models, and geospatial analysis. The effects of atmosphere-ocean circulation anomalies, topographic relief, vegetation type, soil texture, and demographic and socioeconomic factors on the vulnerability of natural and urban vegetation to drought were explored. Results suggest that the ecosystems in lower-elevated and warmer areas dominated by moisture-limited vegetation were relatively more sensitive to hotter drought; conversely, the ecosystems in higher-elevated and colder areas dominated by heat-limited vegetation were relatively insensitive to hotter drought. Moreover, the warming climate has led to an increased sensitivity of many vegetation communities to drought, triggering an increase in forest mortality and mountain fire risk. The response of urban vegetation to hotter drought is largely driven by differences in irrigation water use and the underlying socioeconomic factors. In general, urban vegetation in socioeconomically advantaged communities is relatively insensitive to drought; vegetation in disadvantaged communities is more sensitive to drought, more prone to vegetation degradation, and less able to suppress heat waves. In addition, climate warming is further strengthening the polarization trend of green vegetation in many big cities, leading to the intensification of environmental injustice in urbanized areas. In the future, advocating and developing more rational policies for water allocation and urban green space management may help promote environmental justice and overall resilience to climate change in our cities and societies.